During several years recently, the reduction in the size and high-integration of devices have been accelerated as semiconductor technologies have been developed. In case of memory semiconductors, since the position of a capacitor is changed from CUB (Capacitor Under Bit Line) to COB (Capacitor Over Bit Line) and the form of a capacitor is changed to a cylindrical structure in order to increase the capacity of a capacitor as the degree of integration is increased gradually, and the processes of layering are accompanied successively as multi-layered circuits are used in logic chips, the surface of a wafer is layered after those processes, which brings about many problems in subsequent processes. In order to remove such problems, the Chemical-Mechanical Polishing (CMP) process is introduced so that a wafer is planarized.
One of the processes in which the chemical-mechanical polishing process is used is shallow trench isolation, which is a method of isolation of active elements in the manufacture of semi-conductor devices. This is a method of securing desired active elements through mounting of a silicon oxide film and silicon nitride on silicon, formation of a trench to silicon by etching, gap-filling of the silicon oxide film, and planarization of them by chemical-mechanical polishing. However, the silicon oxide film and silicon nitride film are exposed as the trench is gap-filled with the silicon oxide film and polished chemically and mechanically. The amount of removal of the silicon nitride film will be the greatest if a slurry having a low removal selectivity is used, where a removal selectivity refers to the ratio of the speed of removal of silicon oxide film to that of silicon nitride film. The loss of a silicon nitride film brings about the change in thickness of a field oxide film and reduces an over-polishing margin.
According to U.S. Pat. No. 5,738,800 of Hosali et al., a CMP slurry is comprised of an aqueous medium, abrasive particles, a surfactant, and a compound which complexes with the silicon oxide film and silicon nitride film and has two or more functional groups each having a dissociable proton. According to the above patent, it is deemed that the surfactant used along with the complex in the CMP slurry has an affect on the speed of removing silicon nitride layer from the surface of the complex although it does not perform usual functions of surfactants (i.e., stabilization of corpuscular dispersed bodies, etc.). Chemical interactions between the surfactant and complex are not illustrated. The slurry composition according to the above patent shows more superior selectivity to those of the conventional CMP slurries, but only within a narrow pH range (of about 6 to 7).
Disclosed in U.S. Pat. No. 5,759,917 of Grover et al. is a CMP slurry for selectively polishing a silicon oxide overfill in preference to a silicon nitride film layer during the manufacture of integrated circuits and semiconductors. According to the above patent, a CMP slurry is comprised of carboxylic acid, a salt, and a soluble cerium compound at a pH within the range of about 3 to 11. It is possible to obtain a silicon nitride to oxide removal selectivity of about 5 to 100, but the highest selectivity reported in preferred embodiments is 34.89, and only a selectivity of less than 20 is obtained in most of preferred embodiments materially.
Disclosed in Korean Patent Application No. 2000-074748 is an aqueous slurry comprised of an organic compound (amino acid) having both of a carboxylic acid functional group and the second functional group selected from amine and halogen compounds and abrasive particles in order to be used for removing selectively a silicon oxide film from the surface of the product in preference to a silicon nitride film through chemical-mechanical polishing. However, the selectivity of this slurry tends to be lowered.